Sportrak Thermostat


Hello again everybody.

I was wondering if somebody could just confirm my problem before I go and buy a thermostat and fit it.

While I am driving along the temp gauge goes between 2/3 and the max on the gauge, and then drops back down to around a quarter on the gauge. It keeps on doing it, then it stays around the 1/2.

I was thinking that it could be the thermostat sticking and then opening, allowing the cold water through, shutting and sticking again.

Has anybody else had the same problem?

Thanks for you help.


same as mine i changed the thermostat and also gave the engine a complete flush before hand, run nice and cool now cheers steve


only had mine a couple of weeks - was gonna ask a similar question - my temp gauge can vary a lot - 'norm' seems to be 12 o'clock, however, sunday drivers in front etc causes it to rise to 3/4, a blast down the motorway can see it drop as low as 1/4 - is this norm for a sporty or am i in need of a new stat as well?

cheers, and sorry if ive hijacked the thread!!


ps the vehicles on 91k - had a new engine at 57K according to the history

In your case, I'd say it's a

In your case, I'd say it's a dodgy rad. Check the vanes at the front are not crushed, consequently blocking airflow. Can't be many Sportys running on the original rad, loads here inc. me have had to change them.

Dave with a Sporty

Dave with a Sporty

Several solutions.

Obviously a circulation problem. I assume there is no loss of coolant.
Could be a dodgy thermostat.
Could be a blocked radiator, blocked hose, blocked engine .... try a thorough flush with a hose pipe. You will need to pull a few hoses.
Could be a dodgy water pump. Is the belt tensioned?


I have flushed the rad and the engine and it is clean. There is no coolant being lost. The water pump is only 3 months old and belt is tight. I will get a thermostat tomorrow and see if it helps. Thanks for the advice.

Why are these things never simple?

I fitted the new thermostat today. It has a o-ring. Fitted it all like the handbook says.

Ran the engine, and after 5 minutes it went straight into the red.

Tested thermostat - opened at 82 degrees.

Refitted thermostst and used sealant on the hoses and fittings.

It now went to just over half while idling. When I drove up the road, it went into the red again. Pulled over and stopped it dropped to 2/3.

The top hose was red hot, and the bottom hose was stone cold.

Switched the engine off and after 2 minutes the thermostat opened and the coolant gushed into the engine.

Has anybody got any ideas what is going on? Help

Could it be a dodgy thermostat - at least the old one worked properly most of the time.

Air lock possibly from fittin

Air lock possibly from fitting the new stat?

has it returned to normal running now youve 'burped' the engine - coolant level now dropped etc?


I found the problem. The old stat had a small hole with a pin in to allow the water to vent the excess air through as water flows through the hose.

The new stat didn't have the hole so there was an air lock at the stat.

Got hold of another stat with a hole in, and it now works fine.

A hole in one.

Pleased its fixed ... always match the old against the new !!!!!


Dont drive it if its overheating. The cylinder head will crack!
If the top hose is hot and the bottom remains cold then there is no circulation. The thermostat opens at 82C when tested.
1. Have you fitted the thermostat the correct way up? The wax end gets the heat - so check the flow direction.
2. Assuming the thermostat is fitted the correct way around and the water pump working [does the height of the coolant rise in the expansion tank when the engine is revved/or water hoses feel harder ?] the fault must be a circulation blockage. If the car is approx 10years old its likely to be a blocked radiator. Either its air or dirt. Air blockage unlikely unless the radiators core is rusted. Dirt blockage very likely despite being flushed. The fine tubes in the core of the radiator get blocked with rust. Try reverse flusing or a fushing agent from a motor shop.
Post back the result!